Recessed gas feed distributor apparatus for FCC riser

ABSTRACT

An FCC apparatus may include a distributor disposed in a recess in a wall of the riser for distributing gaseous hydrocarbon feed to a riser. The distributor may be shielded from upwardly flowing catalyst by a shield. An array of nozzles from the distributor may extend through openings in the shield.

BACKGROUND OF THE INVENTION

This invention relates generally to an apparatus for fluid catalyticcracking of hydrocarbons.

DESCRIPTION OF THE PRIOR ART

Fluid catalytic cracking (FCC) is a catalytic conversion process forcracking heavy hydrocarbons into lighter hydrocarbons by bringing theheavy hydrocarbons into contact with a catalyst composed of finelydivided particulate material in a fluidized reaction zone. Most FCCunits use zeolite-containing catalyst having high activity andselectivity. As the cracking reaction proceeds, substantial amounts ofhighly carbonaceous material, referred to as coke, are deposited on thecatalyst, forming spent catalyst. Spent catalyst is continually removedfrom the reaction zone to a regeneration zone. High temperatureregeneration burns the coke from the spent catalyst. The hot regeneratedcatalyst is returned to the reaction zone to contact the hydrocarbonfeed with sufficient heat content to support the endothermic catalyticcracking reaction.

FCC can create a variety of products from heavier hydrocarbons. Often, afeed of heavier hydrocarbons, such as a vacuum gas oil, is provided toan FCC reactor. Various products may be produced, including a gasolineproduct and/or light olefins, such as at least one of propylene andethylene. To produce more light olefins, product cuts from FCC product,such as naphtha, may be recycled to the riser reactor or to anadditional riser reactor for additional catalytic cracking.

It may be desirable to feed these recycled product cuts to a riser in agaseous phase.

It may be desirable to provide a distributor for distributing gaseoushydrocarbon feed to an FCC reactor.

SUMMARY OF THE INVENTION

We have discovered a distributor for feeding gaseous hydrocarbon to anFCC riser.

In an apparatus embodiment, the invention comprises a hydrocarbon feeddistributor for fluid catalytic cracking apparatus. The hydrocarbon feeddistributor comprise a hydrocarbon feed pipe. A tubular header isconnective with the hydrocarbon feed pipe. The header has a roundlongitudinal axis. An array of nozzles extends from the header and arein communication with said hydrocarbon feed pipe.

In an additional apparatus embodiment, the invention comprises a fluidcatalytic cracking apparatus. The apparatus comprises a riser having awall. A recess in the wall surrounds the riser. Lastly, a feeddistributor is disposed in the recess. In a further apparatusembodiment, the distributor comprises a tubular header having a roundlongitudinal axis, and an array of nozzles extending from the header.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational schematic showing an FCC unit.

FIG. 2 is an enlarged cross-sectional view taken of the distributorarrangement of FIG. 1.

FIG. 3 is a cross-sectional view taken along segment 3-3 in FIG. 2.

FIG. 4 is a cross-sectional view taken along arc 4-4 in FIG. 2.

FIG. 5 is an elevational view of a header in the distributorarrangement.

DETAILED DESCRIPTION

This invention relates generally to an improved FCC apparatus.Specifically, this invention may relate to an improved feed distributorand may be useful for FCC operation to spray vaporized feed into areactor riser.

As shown in FIG. 1, an FCC unit 8 may be used in the FCC process.Hydrocarbon feedstock may be sprayed by a distributor arrangement 10into a riser 20 where it contacts catalyst. In general, feedstock may becracked in the riser 20 in the presence of catalyst to form a crackedproduct stream.

A conventional FCC feedstock is a suitable feed to the riser 20. Themost common of such conventional feedstocks is a “vacuum gas oil” (VGO),which is typically a hydrocarbon material having a boiling range of from343° to 552° C. (650° to 1025° F.) prepared by vacuum fractionation ofatmospheric residue. Heavier hydrocarbon feedstocks may also be used inthe present invention. Conventional FCC feedstock may be vaporized andsprayed in the riser by the distributor arrangement 10. In an aspect, astream such as a naphtha stream, perhaps from an FCC product cut, may bevaporized and sprayed into the riser 20 by distributor arrangement 10.An FCC product cut is obtained from an FCC product effluent which isseparated into a variety of product cuts by absorption and/orfractionation. An FCC product cut may be recycled to a riser from whichit was produced or sprayed into a separate, dedicated riser. If an FCCproduct cut is recycled to a riser, conventional hydrocarbon feed may beinjected into the riser 20 by an additional conventional distributor,typically in a lower section 14 of the riser below distributorarrangement 10 which distributes the FCC product cut to the riser. Theadditional conventional distributor may be located in an additionalswaged section (not shown) of the riser.

As shown in FIG. 1, the distributor arrangement 10 is located at aswaged section 12 of the riser between the lower section 14 of the riserhaving a relatively smaller inner diameter and a upper section 16 of theriser having a relatively larger inner diameter than the lower section14. The swage section 12 has an increasing diameter from bottom to topwhich transitions between smaller diameter, lower section 14 and largerdiameter, upper section 16. Regenerated catalyst is delivered to theriser 20 from regenerator standpipe 18. In an embodiment, lift gas whichmay include inert gas such as steam may be distributed by lift gasdistributor 6 to lift catalyst upwardly from the lower section 14 of theriser 20. Alternatively, the distributor arrangement 10 may be situatedlower in the riser 20 and provide gas for lifting which may obviate aseparate lift gas distributor. Vaporous feed sprayed from a distributor10 a in the distributor arrangement 10 contacts lifted, fluidizedcatalyst in the swaged section 12 and moves upwardly in the riser 20into the upper section 16 as the hydrocarbon feed cracks to smallerhydrocarbon cracked products. The cracked products and spent catalystenter the reactor vessel 70 and are then discharged from the top of theriser 20 through the riser outlet 72 and separated into a crackedproduct vapor stream and a collection of catalyst particles covered withsubstantial quantities of coke and generally referred to as spentcatalyst. A swirl arm arrangement 74, provided at the end of the riser20, may further enhance initial catalyst and cracked hydrocarbonseparation by imparting a tangential velocity to the exiting catalystand cracked product vapor stream mixture. The swirl arm arrangement 74is located in an upper portion of a separation chamber 76, and astripping zone 78 is situated in the lower portion of the separationchamber 76. Catalyst separated by the swirl arm arrangement 74 dropsdown into the stripping zone 78.

The cracked product vapor stream comprising cracked hydrocarbonsincluding naphtha, light olefins and some catalyst may exit theseparation chamber 76 via a gas conduit 80 in communication withcyclones 82. The cyclones 82 may remove remaining catalyst particlesfrom the product vapor stream to reduce particle concentrations to verylow levels. The product vapor stream may exit the top of the reactorvessel 70 through a product outlet 84. Catalyst separated by thecyclones 82 returns to the reactor vessel 70 through diplegs into adense bed 86 where catalyst will pass through chamber openings 88 andenter the stripping zone 78. The stripping zone 78 removes adsorbed andentrained hydrocarbons from the catalyst by counter-current contact withinert gas such as steam over the optional baffles 90. Steam may enterthe stripping zone 78 through a distributor 92. A spent catalyst conduit94 transfers coked catalyst, regulated by a control valve, to aregenerator 100. Additionally, a spent catalyst recycle conduit (notshown) may transfer some spent catalyst back to the riser 20 below thefeed distributor arrangement 10 without undergoing regeneration.

As shown in FIG. 1, the regenerator 100 receives the coked catalyst andtypically combusts the coke from the surface of the catalyst particlesby contact with an oxygen-containing gas. The oxygen-containing gasenters the bottom of the regenerator 100 via a regenerator distributor102. Flue gas passes upwardly through the regenerator 100. A primaryseparator, such as a tee disengager 104, initially separates catalystfrom flue gas. Regenerator cyclones 106, or other means, removeentrained catalyst particles from the rising flue gas before the fluegas exits the vessel through an outlet 108. Combustion of coke from thecatalyst particles raises the temperatures of the catalyst. The catalystmay pass, regulated by a control valve, through a regenerator standpipe18 which communicates with the lower section 14 of the riser 20.

Regenerated catalyst from the regenerator standpipe 18 will usually havea temperature in a range from about 649° and about 760° C. (1200° to1400° F.). If air is used as the oxygen-containing gas, the dry air rateto the regenerator may be between about 8 and about 15 kg/kg coke. Thehydrogen in coke may be between about 4 and about 8 wt-%, and the sulfurin coke may be between about 0.6 and about 3.0 wt-%. Catalyst coolers onthe regenerator may be used. Additionally, the regenerator 100 may beoperated under partial CO combustion conditions.

The zeolitic molecular sieves used in typical FCC operation have a largeaverage pore size and are suitable for the present invention. Molecularsieves with a large pore size have pores with openings of greater than0.7 nm in effective diameter defined by greater than 10 and typically 12membered rings. Suitable large pore molecular sieves include syntheticzeolites such as X-type and Y-type zeolites, mordenite and faujasite.Y-type zeolites with low rare earth content are preferred. Low rareearth content denotes less than or equal to about 1.0 wt-% rare earthoxide on the zeolitic portion of the catalyst. Catalyst additives may beadded to the catalyst composition during operation. Medium pore sizedmolecular sieves such as MFI with openings of 0.7 nm or less may beblended in with the large pore molecular sieves to increase productionof lighter olefins. In some cases, only medium pore sized molecularsieves may be used if the feed to the riser is an FCC product cut suchas a naphtha stream.

The riser 20 may operate with catalyst-to-oil ratio of between about 4and about 12, preferably between about 4 and about 10. Inert gas to theriser 20 may be between about 1 and about 15 wt-% of hydrocarbon feed,preferably between about 4 and about 12 wt-%. Before contacting thecatalyst, the hydrocarbon feed may have a temperature in a range of fromabout 149° to about 427° C. (300 to 800° F.), preferably between about204° and about 288° C. (400° and 550° F.). If vaporous naphtha is thefeed, the temperature will be between 30 and 370° C. (86 and 700° F.).If vaporous VGO is the feed, the temperature of the hydrocarbon feedwill be above about 427° C. (800° F.).

The riser 20 may operate in a temperature range of between about 427°and 649° C. (800° and 1200° F.), preferably between about 482° and about593° C. (900° and 1100° F.). The pressure in the riser 20 may be betweenabout 69 and about 241 kPa (gauge) (10 and 35 psig), preferably at about103 kPa (gauge) (15 psig).

The feed pressure drop across the feed distributor arrangement 10 may bebetween about 69 and about 690 kPa (gauge) (10 and 100 psig), preferablybetween about 205 and about 415 kPa (gauge) (30 and 60 psig). The inertgas on hydrocarbon feed from the distributor may be between about 0 andabout 7 wt-%, and preferably between about 1 and 6 wt-%.

FIG. 2 is an enlarged partial elevational view of the feed distributorarrangement 10. The riser 20 includes a wall 22 that may define a swagedsection 12. The wall 22 may be coated with a refractory lining 22 a. Thewall 22 is considered to include the refractory lining 22 a. The wall 22is made of appropriate metal, typically steel; whereas, the lining 22 amay be made of a concrete anchored to the wall 22. The riser 20 includesa recess 24 in the wall 22 that surrounds the riser. In an embodiment,the recess 24 encircles the entire circumference of the riser 20. Therecess 24 may be defined by a convex bulge 26 in the wall 22, so thatthe inner diameter of the riser 20 increases in the recess. In anembodiment, the recess may have a trapezoidal vertical cross section.The trapezoidal vertical cross section may include a lower diagonal side28, a vertical or slightly vertical, upright side 30 and an upperdiagonal side 32. Corresponding refractory linings 28 a, 30 a and 32 a,respectively, are disposed on lower diagonal side 28, upright side 30and upper diagonal side 32, respectively. The convex bulge may belocated in the swage section 12 of the riser 20, so the upright side 30may be slightly angled from vertical and have the same slope as theswage section 12. The feed distributor arrangement 10 is disposed in therecess 24 to protect it from upflowing catalyst. The recess may befilled Kaowool or other material to prevent catalyst infiltration.

The distributor arrangement 10 includes a first distribution device 10 acomprising a tubular header 34 a connective with a hydrocarbon feed pipe36 a. The tubular header 34 a is in downstream communication with thehydrocarbon feed pipe 36 a. The hydrocarbon feed pipe may be the onlyfeed pipe connective with the header 34 a. Vaporized hydrocarbon feedsupplied from a hydrocarbon feed line and perhaps inert purge gas, suchas steam or dry gas, are fed from feed pipe 36 a to the header 34 a. Theheader 34 a has an array 38 a of nozzles 40, 42 extending from theheader. A first side of the header 34 a has a flat face 44 and thenozzles 40, 42 extend from the flat face. The nozzles 40, 42 are tubessuch as cylinders with outlets 40 a, 42 a disposed in the riser 20 andinlets 40 b, 42 b disposed in the header 34 a. Indeed, more than halfand preferably more than two-thirds of the length of the nozzles 40, 42may be disposed in an interior of the header with a remaining lengthextending from the header toward an interior of the riser 20. A firstfrustoconical shield 46 a with an abrasion resistant lining 47 a may besecured to the flat face 44 of the header 34 a such as by welding toshield the header 34 a from abrasive, upwardly flowing catalyst. Thefirst shield 46 a may have an L-shaped flange at its bottom end. Thenozzles 40, 42 extend into the shield through openings 48 in the shield46 a and lining 47 a. The fit between the nozzles 40, 42 and theopenings 48 in the shield 46 should be snug to avoid infiltration bycatalyst.

An imaginary line “A” extends between an innermost intersection 52 of atop of the bulge 26 and the wall 22 of the riser 12 just above the bulge26 and an innermost intersection 54 of a bottom of the bulge 26 and thewall 22 just below the bulge 26 at the same radial position as innermostintersection 52. In other words intersection 52 is defined by the innervertex defined between the upper diagonal side 32 and the wall 22, andintersection 54 is defined by the inner vertex defined between lowerdiagonal side 28 and the wall 22 at the same radial position asintersection 52. Because the refractory linings 22 a, 32 a, 28 a aredisposed inwardly of the walls 22, 32, 28, respectively, theintersections 52, 54 are defined by the inner surface of the refractorylinings. Imaginary line “A” may have a slope that is equal to the slopeof the swage section 12. To protect the nozzles 40, 42 from erosion byabrasive upwardly flowing catalyst, the outlets 40 a, 42 a which aredisposed inwardly of the flat face 44 of the header 34 a, do not extendinwardly of the imaginary line “A.” The imaginary line “A” is containedin an inner surface of the shield 46 a with lining 47 a. Consequently,the outlets 40 a, 42 a do not protrude inwardly in the riser 20 beyondthe first shield 46 a with lining 47 a. The upright side 30 may beparallel to imaginary line “A”.

The distributor 10 a is disposed in the swaged section 12. The swagesection 12 has an increasing diameter from bottom to top which defines aslope. The distributor 10 a defines a longitudinal axis “B” extendingthrough the feed pipe 36 a which may be parallel to the nozzles 40, 42.The longitudinal axis “B” may be perpendicular to imaginary line “A” andupright side 30. The longitudinal axis “B” may be angled from ahorizontal line by angle α which is equal to the slope of the wall 22 inthe swage section 12 from vertical.

A first row of nozzles 40 are disposed above a second row of nozzles 42in the header 34 a. In an aspect, the nozzles 40, 42 are radiallyoriented to direct gaseous feed toward a center of the riser 20.

In operation, a hydrocarbon feed line feeds vaporized hydrocarbon feedto the feed pipe 36 a. The feed pipe feeds the tubular header 34 a. Thetubular header 34 a is filled with the gaseous hydrocarbon feed whichsprays the gaseous hydrocarbon feed through the array of nozzles 40, 42,which may comprise two rows of nozzles 40, 42, into the riser 20. Thefeed may be accompanied with an inert purge gas, such as steam or drygas, to prevent catalyst from infiltrating the distributor if flow fromthe hydrocarbon feed line is interrupted. The distributor 10 a sprayshydrocarbon feed from behind the imaginary line “A”. The frustoconicalshield 46 a shields the distributor 10 a from catalyst flowing upwardlyin the riser.

The distributor arrangement 10 may comprise a second distributor 10 bdisposed below the first distributor 10 a. The second distributor 10 bis in all respects the same as the first distributor 10 a, except it maybe rotated out of phase with the first distributor 10 a by 90 degrees inthe horizontal plane and may have a slightly smaller diameter due to itslocation lower in the swaged section 12 and the recess 24 of smallerdiameter. The second distributor 10 b comprises a tubular header 34 bwith an array 38 b of nozzles 40, 42 extending from a flat face 44. Asecond frustoconical shield 46 b with an abrasion resistant lining 47 bmay be secured to the flat face 44 of the header 34 b such as by weldingto shield the header 34 b from abrasive, upwardly flowing catalyst. Atop edge of second shield 46 b is slidably engaged with an L-shapedflange on the bottom edge of the first shield 46 a. Shields 46 a and 46b with respective linings 47 a, 47 b are independently secured to allowfor independent thermal expansion. The imaginary line “A” is containedin an inner surface of the shield 46 b with lining 47 b. The nozzles 40,42 extend through openings 48 in but not beyond the second shield 46 bwith lining 47 b and imaginary line “A”.

The distributor arrangement 10 may also comprise a third distributor 10c disposed opposite to the first distributor 10 a. The third distributormay be disposed at the same height as the first distributor 10 a. Thethird distributor 10 c is in all respects the same as the firstdistributor 10 a, except it is rotated out of phase with the firstdistributor 10 a by 180 degrees in the horizontal plane. The thirddistributor 10 c comprises a tubular header 34 c with an array of 38 cnozzles 40, 42 extending from a flat face 44. A third frustoconicalshield 46 c with an abrasion resistant lining 47 c may be secured to theflat face 44 of the header 34 c such as by welding to shield the header34 c from abrasive, upwardly flowing catalyst. The third shield 46 c mayalso have an L-shaped flange at its bottom end. A top edge of secondshield 46 b is slidably engaged with the L-shaped flange on the bottomedge of the third shield 46 c. The nozzles 40, 42 extend into the shield46 c through openings 48 in the shield 46 c and lining 47 c. The fitbetween the nozzles 40, 42 and the openings 48 in the shield 46 c shouldbe snug to avoid infiltration by catalyst. The nozzles 40, 42 extendthrough openings in but not beyond the second shield 46 c with lining 47c and imaginary line “A′”. Imaginary line “A′” has the same definitionas imaginary line “A” except it is drawn on the opposite side of theriser 20 in FIG. 2 for illustrative purposes.

The distributor arrangement 10 may also comprise a fourth distributor 10d disposed opposite to the second distributor 10 b and below the thirddistributor 10 c, but it cannot be viewed in FIG. 2.

FIG. 3 is a cross-sectional view of FIG. 2 taken at segment 3-3 showingthe first and third distributors 10 a and 10 c. The header 34 a of thefirst distributor 10 a has a round longitudinal axis “C”. By roundlongitudinal axis, it is meant that the axis can be circular or arcuatewith circular being preferred. The header 34 a of the first distributor10 a extends only partially around the riser 20 in the recess 24 whichis shown to be an annular groove. The hydrocarbon feed pipe 36 aconnects to a middle 60 a of the header 34 a and the header has tworounded arms 62 a and 64 a extending from each side of the middle 60 a.Only the top row of nozzles 40 can be seen in FIG. 3. The frustoconicalshield 46 a with liner 47 a extends only partially around the riser 20nearly coextensive with the first distributor 10 a. Ends of the shield46 a may be equipped with L-shaped flanges.

The header 34 c of the third distributor 10 c also has a roundlongitudinal axis “C”. The header 34 c of the third distributor 10 cextends only partially around the riser 20 in the recess 24 and opposesthe header 34 a of the first distributor 10 a. The hydrocarbon feed pipe36 c connects to a middle 60 c of the header 34 c and the header has tworounded arms 62 c and 64 c extending from each side of the middle 60 c.The arm 62 a of the header 34 a of the first distributor 10 a has an endadjacent to an end of the arm 62 c of the header 34 c of the thirddistributor 10 c, and the arm 64 a of the header 34 a of the firstdistributor 10 a has an end adjacent to an end of the arm 64 c of theheader 34 c of the third distributor 10 c. The frustoconical shield 46 cand liner 47 c extends only partially around the riser 20 nearlycoextensive with the third distributor 10 c. Ends of the shield 46 c mayslidably engage L-shaped flanges of shield 46 a to allow for thermalexpansion.

FIG. 4 is a cross-sectional view of FIG. 2 taken at arc 4-4 showing thesecond and fourth distributors 10 b and 10 d. The header 34 b of thethird distributor 10 b has a round longitudinal axis “C”. The header 34b of the second distributor 10 b extends only partially around the riser20 in the recess 24 which is shown to be an annular groove. Thehydrocarbon feed pipe 36 b connects to a middle 60 b of the header 34 band the header 34 b has two rounded arms 62 b and 64 b extending fromeach side of the middle 60 b. Only the top row of nozzles 40 can be seenin FIG. 4. The frustoconical shield 46 b and liner 47 b extends onlypartially around the riser 20 nearly coextensive with the seconddistributor 10 b. Ends of the shield 46 b may be equipped with L-shapedflanges.

The fourth distributor 10 d is first illustrated in FIG. 4. A header 34d of the fourth distributor 10 d has a round longitudinal axis “C”. Theheader 34 d of the fourth distributor 10 d extends only partially aroundthe riser 20 in the recess 24 and opposes the header 34 b of the seconddistributor 10 b. A hydrocarbon feed pipe 36 d connects to a middle 60 dof the header 34 d and the header has two rounded arms 62 d and 64 dextending from each side of the middle 60 d. The arm 62 b of the header34 b of the second distributor 10 b has an end adjacent to and end ofthe arm 62 d of the header 34 d of the fourth distributor 10 d, and thearm 64 b of the header 34 b of the second distributor 10 b has an endadjacent to an end of the arm 64 d of the header 34 d of the fourthdistributor 10 d. The frustoconical shield 46 d and liner 47 d extendsonly partially around the riser 20 nearly coextensive with the fourthdistributor 10 d. Ends of the shield 46 d may slidably engage L-shapedflanges of shield 46 b to allow for thermal expansion.

FIG. 5 is an elevational view of the header 34 a of the distributor 10a. The header 34 a includes the middle section 60 a flanked by arms 62 aand 64 a. The two rows of nozzles 40, 42 are grouped among the middle 60a and the arms 62 a, 64 a of the header 34 a. The nozzles 40, 42 may bedisposed in an array 38 a having a triangular pitch. The other headers34 b, 34 c and 34 d may have a similar configuration. The two higherheaders 34 a and 34 c may have a greater circumferences and consequentlymore nozzles 40, 42 than the two lower headers 34 b, 34 d because thediameter of the swage section 12 increases with height.

Greater or less distributors 10 a-10 d are contemplated. In other words,more or less distributors may be provided at a given height in the riser20 and more or less levels of distributors are contemplated.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Itshould be understood that the illustrated embodiments are exemplaryonly, and should not be taken as limiting the scope of the invention.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A hydrocarbon feed distributor for fluid catalytic cracking apparatuscomprising: a hydrocarbon feed pipe; a tubular header connective withsaid hydrocarbon feed pipe, said header having a round longitudinalaxis, said hydrocarbon feed pipe connecting to a middle of said headerand said header has two rounded arms extending from said middle; anarray of nozzles extending from said header and in communication withsaid hydrocarbon feed pipe.
 2. The hydrocarbon feed distributor of claim1, wherein said hydrocarbon feed pipe is the only feed pipe connectivewith said header.
 3. The hydrocarbon feed distributor of claim 1,wherein said array of nozzles defines two rows of nozzles.
 4. Thehydrocarbon feed distributor of claim 1, wherein nozzles extend intosaid header.
 5. The hydrocarbon feed distributor of claim 1, wherein afirst side of said header has a flat face.
 6. The hydrocarbon feeddistributor of claim 5, wherein said nozzles extend from said flat face.7. The hydrocarbon feed distributor of claim 1, wherein said nozzlesextend away from said hydrocarbon feed pipe.
 8. The hydrocarbon feeddistributor of claim 1, wherein a shield is secured to said header andsaid nozzles extend into said shield.
 9. A fluid catalytic crackingapparatus comprising: a riser having a wall; a recess in said wallsurrounding said riser; and a feed distributor disposed in said recess,said feed distributor comprising: a tubular header connective with ahydrocarbon feed pipe, said header having a round longitudinal axis, anarray of nozzles extending from said header and a first side of saidheader having a flat face and said nozzles extending from said flatface.
 10. The fluid catalytic cracking apparatus of claim 9, whereinsaid recess is defined by a convex bulge in said wall.
 11. The fluidcatalytic cracking apparatus of claim 9, wherein said hydrocarbon feedpipe is the only feed pipe connective with said header.
 12. The fluidcatalytic cracking apparatus of claim 9, wherein said array of nozzlesdefines two rows of nozzles.
 13. The fluid catalytic cracking apparatusof claim 9, wherein a shield is secured to said header and said nozzlesextend into said shield.
 14. The fluid catalytic cracking apparatus ofclaim 9, wherein said nozzles do not protrude beyond an imaginary lineextending between a top innermost intersection of a bulge defining saidrecess and said wall and a bottom innermost intersection of said bulgedefining said recess and said wall at the same radial position as thetop innermost intersection.
 15. The fluid catalytic cracking apparatusof claim 14, wherein a shield is secured to said header and saidimaginary line is contained in an inner surface of said shield.
 16. Afluid catalytic cracking apparatus comprising: a riser having a wall; arecess in said wall surrounding said riser; a feed distributor disposedin said recess, said distributor comprising a tubular header having around longitudinal axis, and an array of nozzles extending from saidheader; and a shield secured to said header and said nozzles extendinginto said shield.
 17. The fluid catalytic cracking apparatus of claim16, wherein said header extends only partially around said riser.